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 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package java.awt.event;

import java.awt.Container;
import java.awt.Component;

/**
 * A low-level event which indicates that a container's contents
 * changed because a component was added or removed.
 * <P>
 * Container events are provided for notification purposes ONLY;
 * The AWT will automatically handle changes to the containers
 * contents internally so that the program works properly regardless of
 * whether the program is receiving these events or not.
 * <P>
 * This low-level event is generated by a container object (such as a
 * Panel) when a component is added to it or removed from it.
 * The event is passed to every <code>ContainerListener</code>
 * or <code>ContainerAdapter</code> object which registered to receive such
 * events using the component's <code>addContainerListener</code> method.
 * (<code>ContainerAdapter</code> objects implement the
 * <code>ContainerListener</code> interface.) Each such listener object
 * gets this <code>ContainerEvent</code> when the event occurs.
 * <p>
 * An unspecified behavior will be caused if the {@code id} parameter
 * of any particular {@code ContainerEvent} instance is not
 * in the range from {@code CONTAINER_FIRST} to {@code CONTAINER_LAST}.
 *
 * @author Tim Prinzing
 * @author Amy Fowler
 * @see ContainerAdapter
 * @see ContainerListener
 * @see <a href="https://docs.oracle.com/javase/tutorial/uiswing/events/containerlistener.html">Tutorial:
 * Writing a Container Listener</a>
 * @since 1.1
 */
public class ContainerEvent extends ComponentEvent {

  /**
   * The first number in the range of ids used for container events.
   */
  public static final int CONTAINER_FIRST = 300;

  /**
   * The last number in the range of ids used for container events.
   */
  public static final int CONTAINER_LAST = 301;

  /**
   * This event indicates that a component was added to the container.
   */
  public static final int COMPONENT_ADDED = CONTAINER_FIRST;

  /**
   * This event indicates that a component was removed from the container.
   */
  public static final int COMPONENT_REMOVED = 1 + CONTAINER_FIRST;

  /**
   * The non-null component that is being added or
   * removed from the Container.
   *
   * @serial
   * @see #getChild()
   */
  Component child;

  /*
   * JDK 1.1 serialVersionUID
   */
  private static final long serialVersionUID = -4114942250539772041L;

  /**
   * Constructs a <code>ContainerEvent</code> object.
   * <p> This method throws an
   * <code>IllegalArgumentException</code> if <code>source</code>
   * is <code>null</code>.
   *
   * @param source The <code>Component</code> object (container) that originated the event
   * @param id An integer indicating the type of event. For information on allowable values, see the
   * class description for {@link ContainerEvent}
   * @param child the component that was added or removed
   * @throws IllegalArgumentException if <code>source</code> is null
   * @see #getContainer()
   * @see #getID()
   * @see #getChild()
   */
  public ContainerEvent(Component source, int id, Component child) {
    super(source, id);
    this.child = child;
  }

  /**
   * Returns the originator of the event.
   *
   * @return the <code>Container</code> object that originated the event, or <code>null</code> if
   * the object is not a <code>Container</code>.
   */
  public Container getContainer() {
    return (source instanceof Container) ? (Container) source : null;
  }

  /**
   * Returns the component that was affected by the event.
   *
   * @return the Component object that was added or removed
   */
  public Component getChild() {
    return child;
  }

  /**
   * Returns a parameter string identifying this event.
   * This method is useful for event-logging and for debugging.
   *
   * @return a string identifying the event and its attributes
   */
  public String paramString() {
    String typeStr;
    switch (id) {
      case COMPONENT_ADDED:
        typeStr = "COMPONENT_ADDED";
        break;
      case COMPONENT_REMOVED:
        typeStr = "COMPONENT_REMOVED";
        break;
      default:
        typeStr = "unknown type";
    }
    return typeStr + ",child=" + child.getName();
  }
}
